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  • The Role of Training Level and Modality in Pedicle Screw Accuracy.

    Final Number:

    Gary B. Rajah MD; Jung-Min Kim BS; Omar Sadiq BS; Nicholas J. Szerlip MD

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2013 Annual Meeting

    Introduction: Evolving pressure on surgical education necessitates efficient learning of techniques. We evaluated the effect of training year using anatomic, percutaneous fluoroscopy guided and computer navigated techniques on the accuracy of pedicle screw placement to determine if different modalities may be better suited for different levels of training.

    Methods: All instrumented thoracic and lumbar cases performed at Detroit Medical Center by the Neurosurgery Service between August 2012 and March 2013 were included. Cases had hardware verified by post-operative CT. Hardware placement was graded according to (Mirza, Wiggins et al. 2003), grade 0 (within pedicle), grade 1 (<2mm breach), grade 2 (>2mm breach) , and grade 3 (extrapedicular). Pedicle screws were reviewed independently by a resident and attending surgeon. Rates of pedicle breach, EBL, length of case, pedicle size and pedicle starting point were all reviewed. Pedicles were analyzed on PACS system in axial views, using sagittal views to identify the correct level.

    Results: A total of 238 pedicle screws were evaluated in 27 patients. The overall rate of accurate pedicle screw placement among residents defined as Grade 0 or 1 placement was 84.2%. There was no difference in breach rate between modalities. Fluoroscopic cases had significantly less medial breaches (12% ) than anatomic cases (50%) (p .001) and computer navigated cases (73%) (p .0015). EBL values for fluoroscopic, anatomic and computer navigated cases were 425 cc, 720 cc, and 816 cc respectively. Resident level was found to be inversely proportional to breach rate (R squared 0.52). We did not see a clear difference in breach rate for resident level in different modalities.

    Conclusions: Our study supports an inverse relationship between resident experience and pedicle screw accuracy. Fluoroscopic placement of pedicle screws compared to computer assisted and anatomic techniques results in lower medial breach rate.

    Patient Care: This study improves patient care by creating Resident and Attending awareness of the effect of Resident experience on pedicle screw accuracy across three different modalities of screw placement. This study also sets the ground for larger studies which may provide Training Programs measures by resident year for expected performance throughout residency.

    Learning Objectives: By the conclusion of this session, participants should be able identify which modalities in this study have higher medial breach rates, the relationship between increasing resident training and pedicle screw accuracy, as well as possible explanations for this observed finding.

    References: Mirza, S. K., G. C. Wiggins, et al. (2003). "Accuracy of thoracic vertebral body screw placement using standard fluoroscopy, fluoroscopic image guidance, and computed tomographic image guidance: a cadaver study." Spine (Phila Pa 28(4): 402-413.

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